Our roadways and thoroughfares are occupied by many vehicles, including cars, light-duty vehicles, trailers, and semi-trailers. As will sometimes happen, whether as a result of congestion, poor driving conditions, driver error, or for other reasons, rear-impact collisions occur. Rear-impact collisions are especially troublesome when they involve a car or light-duty vehicle and a trailer or semi-trailer. This is true due to the propensity of such vehicles to advance, subsequent to impact, substantially beyond the bumper and into an area beneath the undercarriage of the trailer, causing tremendous property damage, injury, and oftentimes even death.
As a result, U.S. Department of Transportation regulations mandate the installation of rear-impact guards on trailers and semi-trailers with a gross vehicle weight greater than or equal to 4,536 kg (approx. 10,000 lbs.). In the United States, such rear-impact guards must extend horizontally to within 100 mm (approx. 4 in.) of either side extremity of the vehicle. The bottom edge of the horizontal member of the impact guard must be, at all points, within 560 mm (approx. 22 in.) to ground level. Finally, at any height equal to or greater than 560 mm (approx. 22 in.) above ground level, the rearmost surface of the impact guard must be no more than 305 mm (12 in.) forward from the vehicle's rearmost portion. Preferably, the rearmost surface of the impact guard is positioned coplanar with or extending rearward from the transverse vertical plane which defines the rearmost extremity of the vehicle.
Rear-impact guards in the past have consisted of a rigidly-affixed horizontal member suspended from one or more struts attached to the undercarriage of the trailer. Often, these struts include one vertical member and one inclined member coupled to the undercarriage and horizontal member in a triangular formation. The vertical and inclined members must be of sufficient length and rigidity such that when the rear guard sustains an impact, the members are able to bend and deform while absorbing the energy. Such absorption of energy by the vertical and inclined members includes both horizontal and vertical components. Disadvantages with previous designs include their difficulty of removal, lack of deformation or "give," and poor suitability for low-profile vehicles.
Trailers that have a profile lower than a standard trailer, but still above 560 mm (approx. 22 in.) are often unable to utilize the aforementioned design because there is insufficient clearance for inclusion of inclined and vertical members possessing the proper attributes to absorb energy through deformation. If the members are too short, they do not provide sufficient energy absorption to prevent a vehicle from encroaching upon the undercarriage of the trailer. Alternatively, if the strength characteristics of the members are increased, the impact guard becomes too rigid and fails to deform while absorbing energy from the impact. As such, there is a need in the industry for an alternatively-designed rear-impact guard that possess appropriate absorption means for low-profile trailers, semi-trailers, and other vehicles.